In the past, as an image scanning apparatus, there is known an image scanning apparatus that irradiates lights on an original document at the same incident angle from two light sources arranged across the perpendicular of a document glass. As each of the light sources, a light source mounted with a semiconductor light emitting element on a surface of a substrate opposed to the document glass is used. In the image scanning apparatus, when an original document having a level difference such as a bonded document is scanned, lights are irradiated on a level difference portion from both sides by the two light sources located across the level difference portion. Therefore, it is possible to prevent a shadow image from being generated in the level difference portion.
However, in the image scanning apparatus, a warp is caused in the substrate by heat of the semiconductor light emitting element mounted only on one side of the substrate. Since the two light sources are separately provided, costs increase.